When two wires made from different blocks go into another block the Redstone signal does not update properly.
Here is a short video about this: https://youtu.be/SSZa1G5alrw
Thought I was going mad when this happened. Is this intentional or a bug?

If this turn out to be a bug I will be able to provide information like modlist forge version or whatever else is needed.

Definitely, it seem a bug. I tried to replicate the bug but it works fine. Maybe are you using the last version of mod without repeaters? Probably I solved that bug in the version with repeaters and I forget update the version without it. Can you send me the mod's version that are you using?